The present invention has for its object a novel process for improving the qualities or modifying the properties of hair, in particular living human hair, and compositions for treating hair according to this process.
It is already known how to treat textile keratinuous fibers to transform at least a part of the cystine into lanthionine.
Such a treatment is performed in a known way on wool but it cannot be used directly to treat living hair.
Applicants have now discovered, in a manner completely surprising, that when a considerable part of the cystine of the hair is transformed into lanthionine, the qualities of the hair are considerably improved and its cosmetic properties modified.
Hair having undergone this transformation called lanthionization has a different composition and structure from that of normal hair, which gives it interesting new properties.
Thus, lanthionized hair shows a great elasticity when it is in the wet state.
This property is manifested more particularly when lanthionized hair is subjected to combing in the wet state, for example, after shampooing. Then it has been found that lanthionized hair is much more resistant to breaking and that the number of hairs broken during such an operation is clearly less than that of natural hairs, i.e., unlanthionized.
Thus, when, for example, about 70% of the cystine was transformed into lanthionine by the process according to the invention, the number of hairs broken in the wet state was less than half the number of hairs broken in the case of natural hairs.
Further, it has been found that hair subjected to a lanthionization presents a holding after setting which is clearly improved.
Thus, if previously lanthionized hair is set and this setting is compared with that of hair not treated according to the invention, it is found that the holding of the setting is clearly higher in the case of lanthionized hair, in an atmosphere of normal relative humidity, i.e., between about 50 and 70%.
This property is more marked the greater the percentage of cystine transformed into lanthionine.
This characteristic of lanthionized hair means that, after setting, this hair, in an atmosphere of normal relative humidity, resumes its initial form less rapidly than untreated hair.
It has also been found that hair subjected to lanthionization according to the process of the invention presents a greater permeability to the hair treating agents than untreated hair. This improved permeability generally facilitates all capillary treatments, in particular dyeing operations, whether direct dyeing or oxidation dyeing is involved, and bleaching operations. Thus dyeing and bleaching are realized more easily and rapidly than in the case of untreated hair and, in addition, the intensity of the coloring is improved. Further, in treating lanthionized hair with standard capillary products intended to give the hair more suppleness or brilliance, better results are obtained than in the case where the same treatment is applied to unlanthionized hair.
It has also been found that hair, of which a considerable part of the cystine has been transformed into lanthionine, presents an alkaline solubility less than that of natural hair not treated according to the invention. By alkaline solubility is meant the loss of weight by putting in the presence of an N/4 sodium hydroxide solution at a temperature of 65.degree.C.
It should be noted that lanthionization of hair gives it irreversible properties which it keeps during its entire life. This is particularly the case for better holding of a setting which is retained for all successive settings, without it being necessary to use any additional product, even if these later settings are simply done with water.
When the hair is not subjected, during treatment, to any extension, it is necessary, to obtain an interesting improvement of the cosmetic qualities of the hair to transform about 25 to 70% and preferably 35 to 70% of cystine into lanthionine.
To achieve this result, according to the invention, the lanthionization of the hair can be performed by treating the hair in an aqueous medium with a composition having a pH between about 10.5 and 13, for a sufficient time to obtain the desired proportion of lanthionine, keeping the hair in the wet state during the entire treatment.
The compositions having a pH of 10.5 to 13, which can be used for putting into practice the above process, are particularly compositions with a base of alkaline earth or alkali metal hydroxides, whose concentration is a function of the desired pH value.
In the case where the process of the invention is used to treat live hair, not subjecting it to any extension stress, the above process should be practiced at a sufficiently high temperature so that the treatment period is not too long; however, this temperature should be bearable under a heating hood, i.e., it should not exceed 50.degree.C.
Preferably the treatment temperature is between about 25.degree. and 50.degree.C.
The period of treatment, which is a function of the proportion of lanthionine desired, varies according to treatment condition, and particularly according to the composition used and the temperature, as will be explained in detail below.
Therefore, theoretically the period of treatment can vary from a few minutes to a few hours, but, for practical reasons, the characteristics of the process of the present invention have been selected so that the treatment period is not less than 10 minutes or greater than about 60 minutes.
It should be noted that when the composition is a simple aqueous solution of alkaline base, the treatment time should be longer than in the case of a composition in gel or cream form, if it is desired to obtain a comparable degree of lanthionization.
Of course, it is necessary to rinse carefully the hair after treatment.
The proportion of lanthionization which is obtained with the treatment according to the invention (i.e., the percentage of cystine which is transformed into lanthionine) depends on the different characteristics of the treatment.
Thus, the proportion of lanthionization is higher the higher the pH of the composition according to the invention.
The increase of temperature also plays a role in the sense of an increase of the degree of lanthionization.
The influence of these different variables will be illustrated below with concrete examples.
It has also been noted that when the alkaline composition according to the process of the invention is applied to dry hair, the degree of lanthionization is generally higher than when the same composition is applied, under the same conditions, but to hair previously wetted. In case it is possible to apply the composition to dry hair, this makes it possible to apply the process of the invention, lowering either the pH of the composition or the temperature of the treatment period.
According to the invention, an effort should not be made to exceed a degree of lanthionization of 70% which seems to constitute an optimal result for natural hair, i.e., not having previously undergone permanent deformation treatment or bleaching, otherwise the hair is degraded without increasing its degree of lanthionization.
On the other hand, when hair is to be treated that has been previously degraded by prior capillary treatments, i.e., hair whose relative proportion of cystine is less than the normal content by at least about 10%, in this case, the degree of lanthionization applied according to the process of the invention should be reduced correspondingly.
To do this, the period or temperature of treatment or the pH of the composition should be reduced. For example, it would be possible to use compositions having a pH of 10.5 to 12, at a temperature between 25.degree. to 30.degree.C and 50.degree.C for a period between 5 and 20 to 30 minutes.
According to a first embodiment of the invention, the hair is treated in an aqueous medium with a composition of a base of alkaline earth or alkali metal hydroxide having a pH between 12.5 and 13, at a temperature between 40.degree. and 50.degree.C, for a sufficient time to obtain the desired degree of lanthionine, this time being between 10 and 60 minutes. This time generally varies between 20 and 60 minutes in the case where the composition is a simple aqueous solution with an alkaline base.
To maintain the hair in a wet state during treatment, it is possible, for example, to cover the hair with an impermeable cap preventing the loss of water by evaporation.
The nature of the hydroxide giving the composition its pH between about 12.5 and 13 does not have a critical influence on the treatment according to the invention. For example, it is possible to use the following hydroxides: Ca(OH).sub.2, LiOH, NaOH, KOH, or their mixtures, without this list being limiting.
The molar concentration of the alkali or alkaline-earth metal hydroxides or their mixtures in the composition is determined by the desired value of the pH of the composition which should be between 12.5 and 13.
When operating according to the first embodiment of the invention, at about 40.degree.C, the treatment period is generally of the order of 20 to 60 minutes. However, if the composition is a simple aqueous solution with an alkaline base, the treatment period should be at least about 40 minutes.
When operating, according to the first embodiment of the invention, at about 50.degree.C, the treatment period is generally of the order of 10 to 60 minutes (20 to 60 minutes in the case of an aqueous solution).
To illustrate more concretely the influence of temperature and the treatment period, there are given below the results obtained by treating hair with an 0.1 N sodium hydroxide solution (pH = 13). The results are summarized in the following table.
______________________________________ Time Degree of Temperature in .degree.C in Minutes lanthionization in % ______________________________________ 40 40 25 60 29 50 20 27 30 40 60 51 ______________________________________
According to a second embodiment of the invention, it is also possible to perform the lanthionization treatment with compositions with an alkaline-earth or alkali metal hydroxide base, but, in addition, comprising particular substances which have the effect of making it possible to reduce the time, temperature and/or pH of the treatment. Hereafter these substances will be designated as "lanthionization activators."
According to this second embodiment, the hair is treated in an aqueous medium with a composition of alkali or alkaline-earth metal hydroxide base having a pH between about 10.5 and 13, at a temperature between 25.degree. and 50.degree.C, for a sufficient period to obtain the desired degree of lanthionization, this period being around 10 to 60 minutes, said composition containing, in addition, a lanthionization activator selected from the group consisting of electrolytes that are neutral from an oxidation-reduction viewpoint, reducing agents have a limited hydrolytic action on the S-S bonds of the cystine, and cationic surfactants.
The alkali or alkaline-earth metal hydroxides that can be used in the second embodiment of the process of the invention are particularly Ca(OH).sub.2, LiOH, NaOH, KOH, or their mixtures. Their concentration is a function of the desired value of the pH which should be between 10.5 and 13.
The neutral electrolytes from the oxidation-reduction viewpoint can be inorganic electrolytes, such as alkali metal halides such as, for example, sodium chloride, or lithium bromide, or alkaline-earth metal halides such as calcium chloride, or again alkali or alkaline-earth metal sulfates such as sodium, potassium or calcium sulfate.
Preferably, they are used in a concentration up to 5 moles per liter.
The electrolytes, neutral from an oxidation-reduction viewpoint, can also be organic electrolytes such as guanidine carbonate, and can preferably be used in a concentration up to one mole per liter.
The reducing agents having a limited hydrolytic action on the S-S bonds of the cystine can be made up for example, of alkali or alkaline-earth metal sulfides, in a concentration of up to 3 .times. 10.sup.-.sup.2 moles per liter, or again of alkali or alkaline-earth metal sulfites in a concentration between 10.sup.-.sup.3 and 10.sup.-.sup.1 moles per liter.
The activators, made up of cationic surface active compounds, can be made up, for example, of cetyl trimethylammonium bromide (known under the trademark Cetavlon) in a concentration of up to 3 .times. 10.sup.-.sup.2 moles per liter, or a quaternary ammonium hydroxide such as that known as Hyamine 10 X, in a concentration of up to 10.sup.-.sup.1 moles per liter.
It should be noted that according to the second embodiment of the process of the invention, treatment of the hair can be performed either without heating, i.e., in practice, at about 25.degree.-40.degree.C, or with heating between 40 and 50.degree.C. In this latter case, the heating is obtained under a heating hood, the hair being covered with an impermeable cap to prevent any loss of water.
The operating condition of the treatment according to the second embodiment of the invention, as a function of the temperature at which it is desired to operate, can be made precise as indicated below.
When operating between 25.degree. and 40.degree.C, the treatment period is generally of the order of 30 and 60 minutes.
When operating between 40.degree. and 50.degree.C, the treatment period is generally of the order of 10 to 60 minutes.
To illustrate more concretely the influence of temperature and the treatment period and the influence of the presence of a lanthionization activator, there are given below the results obtained by treating hair with a 0.1 N sodium hydroxide solution, to which has been added lithium bromide so that the LiBr concentration is between 0.1 M and 3.8 M, which has the effect of making the pH vary from 12.8 to 10.5. The results are summarized in the following table.
__________________________________________________________________________ Temperature Time in Degree of lanthionization in % in .degree.C minutes pH 10.5 pH 11 pH 11.5 pH 12 pH 12.8 __________________________________________________________________________ 25 40 27 50 25 60 29 35 38 40 30 25 25 28 50 25 60 30 45 48 50 10 35 36 36 37 20 50 45 30 47 60 53 65 55 55 __________________________________________________________________________
The present invention also has for its object the novel industrial product made up of a composition for treating hair according to the process defined above, said composition being characterized by the fact that it has a pH between about 10.5 and 13, and that it contains in an aqueous medium at least an alkali or alkaline-earth metal hydroxide and at least a lanthionization activator selected from the group consisting of electrolytes, neutral from an oxidation-reduction viewpoint, inorganic or organic, reducing agents having a limited hydrolytic action on the S-S bonds of the cystine, and cationic surfactant compounds.
The lanthionization activators are present in amounts as indicated above in the compositions of the invention.
The compositions used according to the invention are advantageously in gel or cream form, with sufficient consistency for the composition to be retained naturally on the hair. In this way, there is prevented a considerable evaporation of the aqueous phase which should subsist to assure practice of the process according to the invention. Actually, according to the invention, it is necessary that the hair be kept in the wet state during the entire treatment period.
Further, the cream or gel should be such that the aqueous phase containing the active substances can come in contact and assure impregnation of the hair.
These emulsions constituting the composition are preferably of the oil in water type.
The compositions according to the present invention are prepared according to the usual methods.
They comprise adjuvants usually used in creams or gels, particularly, polyoxyethylene glycols; other polyethers such as nonylphenol polyethoxyethers; fatty acids such as oleic acid; fatty alcohols such as oleyl alcohol; hydroxyethyl cellulose, and the like.
It should be noted that according to the invention the alkaline composition which makes it possible to achieve the transformation of cystine into lanthionine should be without alcohol or with a slight alcohol content (preferably less than 10%) because the presence of alcohol increases the alkaline solubility of the hair.
The treatment according to the invention is clearly distinguished from standard processes of hair treatment such as those which are used for permanent deformations, oxidizing dyeings, or bleachings, because these treatments are always carried out under conditions different from those according to the invention, and they practically always take place in a medium that is both alkaline and oxidizing.
At the time of these standard treatments, it seems that a certain amount of keratocystine (K-S-S-K) is temporarily transformed into lanthionine (K-S-K), but since the nascent lanthionine is very sensitive to oxidizing agents (peroxide, persulfate, etc.) it immediately gives rise to the formation of oxides corresponding to the formula K-SO-K and K-SOO-K, K being the residue of the keratinous molecule.
Such a transformation is irreversible and at the time of hydrochloric hydrolysis of hair treated by standard processes, comprising such oxides, these latter decompose to give cysteic acid (KSO.sub.3 .sup.-).
On the other hand, when hair is treated according to the invention a considerable formation of lanthionine is obtained which is stable in regard both to alkaline and acid agents.
Hair treated according to the invention shows, after having undergone a hydrochloric hydrolysis, a degree of lanthionine which remains unchanged and which is always reproducible under precise dosing conditions.
There is indicated below the way to determine the degree of lanthionization under consideration in the present application.